Seventeen men and one woman joined in the carefully staged demonstration in the heart of Beijing’s leafy diplomatic district, chanting slogans asserting China’s claim to the Tiaoyutai islands and demanding Japan vacate the East China Sea.

About 100 police officers surrounded the protesters and blocked reporters from approaching or interviewing them. Protesters were refused permission to distribute a statement and dispersed quickly after the 15 minute demonstration.

The protest follows the sinking of a Taiwanese boat off the Japan-administered islands last week after a collision with a Japanese coast guard vessel. Beijing claims both Taiwan and the Tiaoyutai chain, called Senkaku by Japan, as its sovereign territory.

The demonstration also came just hours ahead of the announcement of an agreement on joint Chinese-Japanese development of undersea gas deposits in the East China Sea, an issue that has long dogged relations, stirring nationalist indignation among parts of the Chinese public.

While the protesters did not mention that agreement by name, they demanded Japan “clear out” of the area, in which Japan and China have overlapping exclusive economic zones.

“The East China Sea is Chinese. Tiaoyutai is Chinese,” they chanted. One man read a letter of protest before dropping it in the embassy’s mail slot.

Chinese authorities almost never permit protests, and it wasn’t clear why they gave their approval this time. China’s communist leaders are extremely sensitive to anti-Japanese feelings among the public. Many Chinese continue to resent Japan over its brutal invasion and occupation of much of China last century, feelings kept raw by communist propaganda and the education system.

Despite that, relations with Tokyo have improved vastly since violent anti-Japanese protests broke out in Shanghai, Beijing and other cities in the summer of 2005, although incidents such as the most recent flare up over Tiaoyutai continue to show how delicate that balance remains.

“The Tiaoyutai incident is something that neither government expected to happen. The Chinese government can only repeat their stance on the issue and try to play it down,” said Liang Yunxiang, a Japan expert at Peking University’s School of International Studies.

Inflamed anti-Japanese feelings would narrow the government’s room for maneuver, Liang said.

“The government will be forced to take some action, which would definitely have a negative effect on solving other problems,” Liang said.

Japan added the uninhabited chain to its territory in 1895, saying no nation exercised a formal claim over them.